This invention generally relates to solderless printed wiring board modules, and is specifically concerned with a system and method for implementing a wiring change with respect to any electrical component detachably connected to a PWB.
Solderless printed wiring board modules are known in the prior art. Such modules comprise a printed wiring board (PWB) having one or more arrays of contact pads (known as "footprints" in the art), a heat-conductive guide plate assembly having a plurality of apertures that are registrable with the pattern of contact pad arrays on the PWB, each aperture being matable with an electronic component, and an interface formed from a piece of compliant, insulative sheet material that is receivable within one of the apertures of the guide plate. The interface includes a plurality of resilient electrical connectors (called "button connectors" in the art) that are registrable with the contact pads of the PWB When the interface is dropped into one of the apertures of the guide plate. Each of these button connectors is formed from a small, springy cylinder of randomly compressed, thin gauge copper-beryllium wire that has been gold plated. Each of these connectors is frictionally received within a through-hole present in the interface.
In operation, the interface is first dropped into one of the apertures of the guide plate assembly. The shape of the outer edge of the compliant sheet material forming the interface is matable within the aperture in the guide plate, and the button connectors are registrable with the contact pads of the PWB such that the lower end of each of the connectors engages one of the pads in ,the PWB. An electrical component is next dropped into the aperture of the guide plate. The shape of the outer edge of the electrical component is likewise matable with the aperture in the guide plate assembly such that its contact pads become aligned with the upper ends of the button connectors held by the interface. When the electrical component is compressed downwardly toward the PWB, each of the resilient button connectors provides a positive, spring contact between the pads of the PWB, and the corresponding pads of the electrical component. Such a PWB module is disclosed and claimed in U.S. Pat. No. 4,933,808, invented by Messrs. Robert Bourdelaise, David Harris and Roald Horton, and assigned to the Westinghouse Electric Corporation.
Such solderless PWB modules provide a great many advantages over conventional, soldered printed wiring board modules. The elimination of the soldering operation between the pads of the electrical components and the printed wiring board eliminates up to 67 percent of the required assembly time, and further greatly reduces the possibility of component damage due to overheating. Such solderless PWB modules may provide a higher degree of reliable interconnection between the electric-al components and the printed wiring boards, as there is no possibility of defective connections occurring as a result of solder splattering or defective solder joints. Because of the need for inspecting finished solder joints, soldering encouraged perimeter-type connections to be made between the electrical component and the printed wiring board, where the finished connections could be seen. In instances where the electrical component had a large density of leads projecting out around its perimeter, the margin for error became very small for the proper soldering of each of these leads to its respective contact pad on the PWB as the distance between the leads became small. By contrast, the advent of solderless PWB modules which utilizes a sheet-like interface that holds an array of small, springy button connectors to create electrical contact between the pads of the component and the PWB made it much more practical to spread these connections out in an area array pattern, where the connections are uniformly spaced apart from one another throughout the entire area under the component, as opposed to locating these connections to only around the perimeter, thereby reducing the probability of an assembly error. The elimination of soldering in solderless PWB modules also advantageously obviates the need to use fluorocarbon solvents which contribute to the degradation of the ionosphere. Finally, such solderless PWB modules have much more effective heat sink properties than their prior art counterparts, and are far easier to test, repair and replace components on.
Unfortunately, until the advent of the present invention, there was no known way to implement wiring changes in such solderless PWB modules. This is a significant limitation, as it adversely effects the high degree of versatility and flexibility enjoyed with such modules.
It is therefore an object of the present invention to provide both a system and a method for implementing a wiring change with respect to an electrical component detachably connected to a solderless PWB modules that is both fast, efficient and easy.
It is a further object of the invention to provide such a system and technique that obviates or at least minimizes the need for any soldered connections within the PWB module, in order that the advantages associated with the elimination of soldering might be substantially preserved.
Still another object of the invention is to provide a system and method for making wiring changes in PWB modules that utilizes inexpensive components and techniques.
Finally, it is an object of the invention to provide a system and method in which more than one wiring change may be made on more than one occasion in a fast, simple and economical manner both between electrical components such as surface mounted components and PWBs as well as between two or more PWBs of different modules.
As used herein, the term "electrical component" includes not only surface mounted components (SMCs) such as packaged integrated circuits, and individual components such as capacitors, transistors, diodes or the like, but also the PWBs of other modules.